STAUROMEDUSAE UK
An online guide to the Stalked jellyfish (Stauromedusae) found
around the coastal waters of the United Kingdom and Ireland.
Includes notes on their identification, and where and how to find them.
LUCERNARIA AT SCARBOROUGH.
JOHN IRVING, M.D., Scarborough,
Lucernaria campanulata has made its appearance in South Bay, Scarborough. As far as I know it has not hitherto been found in this locality. I saw it for the first time on 7th May, at low tide, in an open tidal pool bottomed with flat rocks variegated by red, green, and brown weeds. In the intersecting rock channels, where the depth of water varied from twelve to eighteen inches, the oak-tree seaweed, Halidrys siliquosa, with its long floating fronds, was plentiful. Individual lucernarians — about thirty altogether — were sparsely distributed over a fairly wide area, securely attached by their
Lucernaria campanulata.
Fig. 1. - Lucernaria, 1/2 nat. size, attached by (a) contracted aboral disc to Halidrys siliquosa;
(b) bell-shaped body; (c) claw-shaped tentacular tufts surrounding oral entrance.
Fig. 2. - Diagram of internal arrangement; (t) tentacular tufts; (m) mouth; (s) sperm masses: (o) genital bands showing white egg masses in central position.
Fig. 3. - Extended pedicle (p) with anemone-like disc (d).
Fig. 4. - Cluster of capitate tentacles from young specimen as seen under microscope (1 1/4in. objective).
aboral discs to Halidrys branches, and only discernible by careful scrutiny owing to the perfect harmony of their environment, and the fact that a large patch of seaweed rarely yielded more than one specimen. Not one was discovered unattached, or adherent to rock, or any other species of seaweed. In colour they resembled ordinary beadlet anemones. Dark brown forms were most common, but reddish-brown, red, and deep green were in evidence. One very young specimen, about a quarter of an inch long, white and semi-translucent, except for numerous light-brown lines and spots scattered over bell and stalk, was valuable for microscopic study. Living, as it did, for more than a fortnight in a glass cell, containing fresh seawater only, without any kind of weed or any apparent source of colouring matter, the pigmentation lines and spots were observed to darken in tint, grow in size, and invade all the tentacles. Detached from its natural anchorage, the little creature was for several days very restless, but there was no attempt to change its place by pulsation or otherwise. The somewhat flattened bell, lying on the bottom of the glass, if uninterfered with, displayed movements of body, of stalk, and of tentacles. The stalk was often considerably elongated and smooth in outline. It appeared to be in search of a suitable lodging place, curling itself first to one side, then to the other, now downwards, then upwards, revealing its anemone-like base or disc and aperture. When the stalk was touched with a pencil it immediately contracted to a third, or even a quarter of its length, withdrawing its disc and wrinkling itself into transverse folds and undulating margins, clearly indicating a sensitive and highly muscular organization. The bell-shaped body exhibited definite muscular movements consisting of expansion or contraction of one or more segments, the power to depress, to raise, or to turn the bell bodily over on to its tentacles. Capitate tentacles, few in number in this young specimen compared with an adult, were in groups of four, marking the summit of each of the eight cleft digitate processes which arise from the margin of the bell (Fig. 4). Each tentacle, however, had an absolutely independent range of movement apart from its fellows, or it could unite with those of the entire tuft in concerted action. At the end of a week, failing in its quest for a stem of Halidrys, the young lucernarian actually attached its disc to the glass and there remained firmly adherent till it died.
Lucernarians are classed amongst Jelly-fishes as Stauromedusae, and while there are distinct points of resemblance to Medusae, the general endowment of the race seems more in consonance with actinozoa. The pulsatile swimming so characteristic of Medusae is non-evident, nor does the life-history reveal metamorphosis. On the other hand they possess a peculiarly sensitive aboral disc which in the case of Lucernaria campanulata always finds out Halidrys siliquosa, and apparently no other seaweed, for mooring purposes. Once attached to this, the muscular pedicle serves not merely as a suspender, but also as a complex lever for directing the body. Individuals are usually found on the floating weed, either on, or very near, the surface of the water where crustaceans and other small organisms abound. They are very voracious, even in captivity, and greedily seize with one or more tufts of tentacles anything coming in contact with them. A human finger, or the point of an ivory paper-knife, is caught with sufficient energy to permit an experimenter to drag the lucernarian about for a considerable time before it relaxes its hold upon its hoped-for victim. One has to consider the fact that in an adult there are eight grasping tufts, that each tuft bears from eighty to a hundred capitate tentacles, every one charged with nematocysts or stinging-thread cells, and that the conjoint use of six hundred to eight hundred stinging tentacles proves a formidable battery in capturing prey. A full-grown specimen measures one and a quarter inches in length and about one and a quarter inches in diameter across the expanded bell mouth. The interior appearance of the bell is shown in the diagram. Fig. 2, where the genital bands, containing numerous white masses of eggs, radiate from the mouth to alternate marginal bays. The oral cavity, said to be square-shaped, is not really so, but having four attachments corresponding to the genital bands, it produces an impression of squareness. This mouth is very extensile and moveable; it can be swayed about freely, altered in shape, thrust outwards or withdrawn, according to need. As in anemones there is a mesenteric cavity and gastral filaments for digestive purposes. The peculiar hand, or claw-like shape of the eight tentacle-bearing processes, makes up for the lack of a circumoral musculature as provided in anemones, for, singly, each claw can convey food within, and, jointly, the turning in of eight such claws closes the exit, and prevents escape, till the mouth organ engulfs the quarry.
All specimens of Lucernaria campanulata examined were charged with egg masses, and it is not unreasonable to
suppose their advent here is connected with spawning, and that another opportunity of securing them may be far distant. Last year, for instance, the sea-hare, Aplysia punctata, occurred in phenomenal abundance, deposited countless egg coils, and disappeared. This year only one small sea-hare has been seen.
The Lucernarians of the South Coast (Haliclystus octoradiatus) differ in many respects from Lucernaria campanulata. They choose the long green blades of Zostera for attachment instead of Halidrys siliquosa. Zostera beds are not found at Scarborough; Haliclystus is conspicuous by its absence.
